A device configured by making an electrode pair facing each other so as to have a nanogap therebetween and by placing a nanoparticle or molecule in the nanogap has a switching and memory functions, and is thus considered promising as a new device. The inventors aim to assemble a single electron transistor (SET) by introducing a chemically synthesized metal nanoparticle into nanogap electrodes produced by electroless gold plating, thus making an SET integrated circuit that operates at room temperatures (Non-patent Literature 1). The inventors have also succeeded in producing nanogap electrodes having a gap length of 5 nm or shorter at an yield of 90% (Non-patent Literature 2), and furthermore developed a “molecular ruler electroless gold plating (MoRELGP)” method using a surfactant agent molecule as a template, thus establishing a technology for producing nanogap electrodes having a gap length of 2 nm with high reproducibility (Patent Literature 1).